<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>AJAX POST 请求</title>
</head>
<style>
    #result {
        width: 200px;
        height: 100px;
        border: solid 1px #903;
    }
</style>

<body>
    <div id="result"></div>
    <script>
        //获取元素
        const result = document.getElementById('result');
        //绑定事件
        result.addEventListener("mouseover", function() {
            //1.创建对象
            const xhr = new XMLHttpRequest();
            //2.初始化 设置请求方法与url
            xhr.open('POST', 'http://127.0.0.1:8000/server');
            // 设置请求头
            // xhr.setRequestHeader('头的名字','头的值');
            // xhr.setRequestHeader('Content-Type', 'application/x-www-from-urlencoded');
            //3.发送
            // xhr.send('a=100&b=200');
            xhr.send('a:100&b:200');
            //4.事件绑定
            xhr.onreadystatechange = function() {
                //判断
                if (xhr.readyState === 4) {
                    if (xhr.status >= 200 && xhr.status < 300) {
                        //处理服务端返回的结果
                        result.innerHTML = xhr.response;
                    }
                }
            }
        });
    </script>
</body>

</html>